• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.6D
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• pp.809-817
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• 2008

This paper deals with the development of ViscoElastic Continuum Damage Finite Element Program (VECD-FEP++) and its verification with the results from both field and laboratory accelerated pavement tests. Damage characteristics of asphalt concrete mixture have been defined by Schapery's work potential theory, and uniaxial constant crosshead rate tests were carried out to be used for damage model implementation. VECD-FEP++ predictions were compared with strain responses (longitudinal and transverse strains) under moving wheel loads running at different constant speeds. To this end, an asphalt pavement section (A5) of Korea Expressway Corporation Test Road (KECTR) instrumented with strain gauges were loaded with a dump truck. Also, a series of accelerated pavement fatigue tests have been conducted at pavement sections surfaced with four asphalt concrete mixtures (Dense-graded, SBS, Terpolymer, CR-TB). Planar strain responses were in good agreement with field measurements at base layers, whereas strains at both surface and intermediate layers were found different from simulation results due to the complexity of tire-road contact pressures. Finally, fatigue characteristics of four asphalt mixtures were reasonably described with VECD-FEP++.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.4C
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• pp.231-238
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• 2008

A column testing device capable of measuring the electrical resistivity of soil at 3 different locations was developed to verify applicability of bulk electrical conductivity (BEC) breakthrough curves in monitoring contaminant transport. Tracer injection tests were conducted with three different types of saturated sands to obtain average linear velocities and longitudinal hydrodynamic dispersion coefficients based on BEC breakthrough curves and effluent solute breakthrough curves. Comparative analysis of transport parameters obtained from curve fitting the results into the analytical solutions confirmed the validity of resistance measurements in estimating time-continuous resident solute concentration. Under the assumption that a linear relationship exists between ${\sigma}_{sat}-{\sigma}_w-C$, the BEC breakthrough curves are able to effectively reduce the laborious and time-consuming processes involved in the conventional method of sampling and analysis. In order to reduce possible uncertainties in analyzing the BEC breakthrough curves, it was recommended that resistance measurements take place nearby the effluent boundary. In addition, a sufficient electrical contrast or difference in the electrical conductivity of the influent and the saturating solution is required to conduct reliable analysis.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.5A
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• pp.673-683
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• 2008

This study improved the existing method of using the longitudinal strain and concept of influence line to develop Bridge Weigh-in-Motion system without axle detector using the dynamic strain of the bridge girders and concrete slab. This paper first describes the considered algorithms of extracting passing vehicle information from the dynamic strain signal measured at the bridge slab, girders, and cross beams. Two different analysis methods of 1) influence line method, and 2) neural network method are considered, and parameter study of measurement locations is also performed. Then the procedures and the results of field tests are described. The field tests are performed to acquire training sets and test sets for neural networks, and also to verify and compare performances of the considered algorithms. Finally, comparison between the results of different algorithms and discussions are followed. For a PSC I-girder bridge, vehicle weight can be calculated within a reasonable error range using the dynamic strain gauge installed on the girders. The passing lane and passing speed of the vehicle can be accurately estimated using the strain signal from the concrete slab. The passing speed and peak duration were added to the input variables to reflect the influence of the dynamic interaction between the bridge and vehicles, and impact of the distance between axles, respectively; thus improving the accuracy of the weight calculation.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.5B
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• pp.535-546
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• 2008

Urbanization results in increased runoff volume and flowrate and shortening in time of concentration, which may cause frequent flooding downstream. The retardation structures are used to eliminate adverse downstream effects of urban stormwater runoff. There are various types of flow retardation measures include detention basin, retention basin, and infiltration basin. In this study, to present a rough standard about location of detention pond for attenuating peak flow of urban area, the runoff reduction effect is analyzed at outlet point when detention pond is located to upstream drainage than outlet. The runoff reduction effects are analyzed under the three assumed basins. These basins have longitudinal shape (SF = 0. 204), concentration shape (SF = 0. 782), and middle shape (SF = 0.567). Numerous variables in connection with the storage effect of detention pond and the runoff reduction effects are analyzed by changing the location of detention pond. To analyze runoff reduction effect by location of single detention pond, Dimensionless Upstream Area Ratio (DUAR) is changed to 20%, 40%, 60%, and 80% according to the basin shape. In case of multiple detention pond, DUAR is changed to 60%, 80%, 100%, 120%, and 140% only under the middle shape basin (SF = 0.567). Related figures and regression equations to determine the location of detention pond are obtained from above analysis of two cases in this study. These results can be used to determine the location of appropriate detention pond corresponding to the any runoff reduction such as storage ratio and peak flow ratio in urban watershed.

• 한국노년학
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• v.31 no.4
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• pp.1135-1153
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• 2011

The study aims to examine the interaction of socio-economic status in education and income in the difference of the level of subjective health, physical health, and mental health of middle-age and the elderly of Korea. While there have been various discussions in precedent study with respect to the serious increase in the number of dependent life alongside with increasing elderly population, research on the health level according to socio-economic status is highly limited, and also how the health level of middle-age and the elderly - whom will arrive at senescence in just a few years - is different. The study aims at analyzing the health level by hierarchy and age based on data targeting the whole nation. As for analysis data, the study utilized 1st Korean Longitudinal Study of Ageing (KLoSA) implemented by Korea Labor Institute, and carried out a path analysis to verify whether income and academic background serve as a parameter to the level of subjective health, physical health, and mental health. As a result, while the subjective health level decreases, the study confirmed an increase in chronic diseases, and extremely low level of mental health when people in middle-age enter the elderly. In addition, the higher the education and income, the more the health levels both on middle-age and the elderly; the result suggests that education background and income have mediated effects in all health level of middle-age and the elderly.

• 한국노년학
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• v.32 no.2
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• pp.577-592
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• 2012

The purpose of this study is to examine which factors determine fall experience among Korean elderly. To achieve this purpose, it uses the Korean Longitudinal Study of Aging(KLoSA), wave 1 and 2. Participants aged 65 from wave 1 were selected. From wave 2, a dependent variable was selected and it was fall experiences since the first interview in 2006. Other than this variable, all independent variables were selected from wave 1. In analyses, x2 or t-test were conducted to examine whether independent variables significantly differ between falls and no falls. Then, since a dependent variable consisted of two categories-falls or no falls, multiple logistic regressions were run. Female, using hearing aid, having two diseases, having three or more diseases, depression, and exercise 5 times/a week or more elevated the odds ratios of fall experience. compared to their reference categories. Particularly, if Korean elderly had three or more diseases or depression, their likelihood of fall experience would have about 2 times higher than their reference categories. In conclusion, health practitioners should make the elderly be recognized how much these risk factors are important to falls. Also, Korean government should support Korean elderly having these risk factors to prevent them from falling.

• 한국노년학
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• v.34 no.2
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• pp.387-407
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• 2014

This study aims to identify the multiple trajectories of depressive symptoms and the characteristics of each trajectory group among the elderly. This study uses five waves of longitudinal data from the Korean Welfare Panel Study (KWPS, 2006-2010). Subjects were older adults aged 60 and over who had completed at least three waves between 2006 and 2010. A total of 4,181 respondents were analyzed. The latent growth mixture model and the multiple logistic regression model were mainly used for data analysis. The major findings were as follows: After controlling for the variables of gender, age, education, marital status, self-assessed health, and poverty, this study identified four different trajectory classes: stable low depressive symptoms (71.8%), high but decreased depressive symptoms (10.6%), moderate but increased depressive symptoms (7.9%), and an increased, then a decreased pattern of depressive symptoms (9.7%). The characteristics of theses trajectories as compared to previous studies were a lower percentage of 'stable low depressive symptoms', no 'persistently high depressive symptoms', and higher level of depressive symptoms. Also, the elderly in the stable low trajectory group had better health status, higher self-esteem and a good relationship with family members, having longer working periods, and more living in non-poverty. In addition, chronic health problems, loss of spouse, and household income differentiated the increased and then decreased pattern from the low stable pattern. Also, age and public pension differentiated the moderated but increased pattern from the low stable pattern. Based on the findings of this study, the researchers suggested political and practical implications for reducing depressive symptoms in later life.

• 한국노년학
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• v.30 no.3
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• pp.709-726
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• 2010

As S. Korea is aging faster than any other industrialized countries, there exists a need to understand how best to improve the quality of life of the elders. The main purpose of this study is to examine the predictors of life satisfaction in the nationally representative sample of adults aged 65 and older (n=4,155) drawn from the Wave I (2006) of the Korean Longitudinal Study on Aging. Hierarchical multiple regression analysis was run to assess the unique explanatory contribution of socio-demographics, social network, activity participation, and physical/psychological health on the life satisfaction. Three separate analyses were undertaken to note differences by education level: older adults with no formal education, those who had completed 9th grade, and those who had completed 12th grade and more. There are three main findings: 1) Physical/psychological health variables such as subjective health, regular exercise, and depression were significant predictors of life satisfaction regardless of education level; 2) While social network and activity participation factors influence life satisfaction of the two lower education groups, such factors don't affect the highest education group; 3) Marital status, household income, and location of residence were significant demographic predictors of life satisfaction regardless of education level. Implications for program development and policy are discussed in this paper.

• 한국노년학
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• v.29 no.3
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• pp.1063-1085
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• 2009

The purposes of this study were to investigate the transition of elderly's welfare service utilization and to examine the factors affecting their utilization as time passed. To solve these research questions, the behavioral model presented by Andersen and Newman(1973) was applied. Using Hallym Aging Panel data consisted of 3 waves from 2003 to 2007, autoregressive modeling and regression analysis were applied for research purposes. The results of this study were as follows; (1) The experiences of welfare service utilization were increasing gradually. The complimentary service for the aged was utilized generally, but leisure service and community service were not used in common. (2) Past experience of service affected service utilization in the following times. (3) The factors affecting older adult's service utilization were different among the types of services. Nonetheless, the factors affecting continuously during the periods were found: age as predisposing factor and area as enabling factor in the complimentary service; area and existence of spouse as enabling factor in leisure service; education as predisposing factor and service cognition as enabling factor in community service. Enabling factor has affected more consistently than other factors. The results showed that special attention should be paid to balanced regional arrangement for welfare resources and the public relation considering the elderly's intellectual level.

• 한국노년학
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• v.29 no.3
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• pp.971-986
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• 2009

This research investigated how the participation of various social activities affects cognitive function in middle-aged and elderly population. To examine the relation between the participation of various social activities and cognitive function, we used data from the Korean Longitudinal Study of Ageing. Social activities were classified into four types as religious ritual, leisure, public association and ascriptive association activities, and MMSE-K score was used to measure cognitive function. Results from multiple regression analyses after adjusting for socio-economic status and health status show that the participation in religious and leisure activities have positive effects on cognitive function in middle-aged and elderly population. Participation in leisure activities in middle-aged male group helps preserve cognitive function, and leisure activity and ritual activity are significantly related to cognitive function in middle-aged female group. Meanwhile the participation in religious and leisure activities have positive effects on cognitive function in elderly male and female group. Based on these findings, we suggest that various programs to support the participation of elderly population in social activities should be developed for healthy life for the elderly.